The 2015-16 television season has yet to begin, but high drama is already taking place behind the scenes. With less than one month until new shows premiere, four network series have seen their showrunners exit.

In the run-up to the fall season, NBC’s “Chicago Med,” Fox’s “The Grinder” and ABC’s “Blood & Oil” and “The Catch” have all parted ways with the original showrunners.

Why the sudden shuffle? In this era of “too much TV” — as FX Networks chief John Landgraf pointed out at this summer’s Television Critics’ Assn. press tour — insiders report the fallout is serious, with most veteran showrunners already booked on one of the 400-plus shows on air.

“Everyone is trying to jockey for position,” said Landgraf, giving a sobering assessment of the state of the TV biz. “We’re playing a game of musical chairs, and they’re starting to take away chairs.”

An industry insider tells Variety, “The business is going through some growing pains in terms of scarcity. There’s more to go around than people available.”

Another consequence of the content glut: Not only is the talent pool shallow, but networks are feeling even more challenged to stay ahead of the competition — on an ever-growing array of platforms.

There’s also increased scrutiny, along with less patience among programmers; letting a show marinate and find an audience is a thing of the past.

Agency types note there’s an enormous amount of pressure on the nets. Part of avoiding the risk of failure is making sure the head honcho is the best fit. “Showrunners are the CEOs of multimillion-dollar enterprises,” one agent points out.

Less-experienced creatives may get the opportunity to sit atop a new show’s throne, but they may not always be fit to rule. That’s where last-minute transitions come in, with network and studio execs forced to face the tough realization that it’s one thing to write a pilot, but a very different thing to run the whole show.

“We need to create a stronger pipeline for the next generation of showrunners,” that same agent adds.

In the case of “The Catch,” co-showrunners and creators Jennifer Schuur and Josh Reims walked away from the midseason project due to “creative differences.” Sources say exec producers are eying Allan Heinberg, who’s well-oiled in the Shondaland machine, having worked on “Scandal” and “Grey’s Anatomy.”

The exit of Schuur — whose producing credits include “Hannibal” — could be a result of networks taking more pitches from young writers who, despite substantial talent, just don’t have the experience of running a show on a weekly timetable.

Seasoned showrunners say that an abrupt change is incredibly hard to pull off when a series is well into production and the clock is ticking on delivery dates.

“When a showrunner is let go because the network or studio decides the creative direction of the show isn’t working in the episodes they’ve seen so far — that’s disastrous. It means all the work you’ve done but haven’t shot yet is all going to be thrown away,” said Bill Lawrence, the comedy honcho who has juggled multiple series in recent years, including NBC’s “Undateable” and CBS actioner “Rush Hour” for the coming midseason. “It’s very rare that a drama or comedy can go on a different creative course successfully without taking three months off. By the time they fire the showrunner, the die is cast and it speaks to disaster.”

ABC’s “Blood & Oil,” created by Josh Pate, who has never run a series solo, had lined up Cynthia Cidre as the showrunner, hoping her experience on “Dallas” would translate. But something clearly didn’t click. Though she’ll remain on the Don Johnson-starrer as an exec producer, “No Ordinary Family” creator Jon Harmon Feldman, who has a relationship with the network, took the reins. Feldman had been brought on as a consultant when it was determined that Cidre, Pate and non-writing exec producer Tony Krantz weren’t leading the show effectively, and he was handed the show within three days.

Meanwhile, veteran producer Greg Malins departed “The Grinder,” Fox’s Rob Lowe sitcom. Sources tell Variety that Malins and creators Andrew Mogel and Jarrad Paul had different visions. It can be tricky when networks marry experienced showrunners with greener writers.

TV lit agents have noted that with so many platforms, creators are coming from various backgrounds, which can result in less-organic marriages. For “Grinder,” this time, Fox sided with the newbies.

One show that will likely get through the fire without many burns is Dick Wolf’s “Chicago Med,” which saw the departure of “CSI” alum Andrew Dettmann. The showrunner slot was quickly filled by established duo Andrew Schneider and Diane Frolov (“The Sopranos”), but even without the quick switch, the medical drama probably would have fared well, with a proven producing team accustomed to the ins and outs of Wolf’s franchises.

Though these showrunners are newly unemployed, it likely won’t be long until another gig opens up given the wealth of programming.

“There are complexities with staffing, but any ecosystem where there are new and exciting opportunities creates healthy competition,” an agent says optimistically.